A number of advances in electronics manufacturing technologies and digital system architectures have resulted in a vast number of business and consumer devices which are capable of generating and communicating information between and amongst each other, consequently increasing the demand for information communication services. Such an increase in the demand for information communication services leads to a corresponding increase in demand for transmission capacities.
One means of providing increased transmission capacity is to provide additional communication network infrastructure. However there is a substantial cost associated with building out additional communication network infrastructure.
Another approach to satisfying the demand for increased information communication capacity is to increase the data rates used in transmitting information across a network. In optical networks, the intersymbol interference due to chromatic dispersion increases quadratically with bit rate. Chromatic dispersion refers to an effect in which the rate at which an optical signal propagates through an optical fiber varies depending on the transmitted wavelength.
At a desired data transmission rate of 40 Gb/sec, the required tighter tolerances, and time-varying changes in dispersion, should be dealt with by compensating for the dispersion.
An optical tunable dispersion compensator (TDC) has utility for long-reach links such as those used in 40-Gb/s systems. Electronic dispersion compensation at 40 Gb/s is not presently suitable for practical use, and yet fiber temperature changes in long links are enough to require the use of a TDC. Importantly, a TDC needs to be colorless, which means that the TDC should have a free-spectral range (FSR) equal to the channel spacing, thereby enabling reconfigurable wavelength-division multiplexing (WDM) networks, and reducing inventory and administrative issues. Another desirable attribute for a TDC for use in, for example, a 40 Gb/s system, is to have a fast tuning speed (e.g., less than about 1 ms) in order to make robust and time-efficient dispersion-control feedback loops. Additionally, single-knob adjustment of the dispersion is desirable, in order to minimize control complexity.
What is needed is a compact, low-power, colorless, tunable dispersion compensator having a fast tuning speed and single-knob dispersion adjustment.